Image capturing devices include cameras, portable handheld electronic devices, and other electronic devices. These image capturing devices can use an automatic exposure mechanism to automatically calculate and adjust exposure settings in order to match as closely as possible a subject's mid-tone to the mid-tone of the photograph. “Correct” exposure may be defined as an exposure that achieves the effect the photographer intended. The purpose of exposure adjustment (in combination with lighting adjustment) is to control the amount of light from the subject that is allowed to fall on the film or image sensor, so that it falls into an appropriate region of the characteristic curve of the film or image sensor and yields a “correct” or acceptable exposure. A photograph may be described as overexposed when it has a loss of highlight detail. This can result in the bright parts of an image being effectively all white. A photograph may be described as underexposed when it has a loss of shadow detail. This can result in the dark areas being indistinguishable from black.
Prior approaches use flat and center-weighted exposure metering for automatic exposure. These approaches are prone to fail in bright outdoor scenes because the automatic exposure mechanism attempts to expose for the bright sky and the darker ground equally. Thus, the subject often appears under-exposed.